1LS400Lexus1

I ordered a recharge kit from AZaircare.com ES-12a after I heard a leak (hissing sound from the dash board area.) I talked to others and many think the evaporator has a leak. I would like to know if anyone knows where the lowside port is, so I can recharge the system. I have heard it is on the passenger side of engine comparment real close to the firewall, but I found two valves. I subscribed to alldata and they show it is the lower and more difficult to get to valve, but I wanted to know if someone knew for sure.

After I add the sealer, is there a method to see if system is truly sealed before added the expensive refridgerant? I have a small AC gauge, but do not know which port to test and what the PSI should read.

Is there an easy way to check the compressor oil level? AllData states that NipponDenso compressor have to be removed from vehicle to check oil level.

1990 LS400 Original compressor R12 freon.